1. Field of the Invention
This invention relates to a data confirmation device for a camera, which makes it possible to readily detect camera exposure data signal values in assembling a camera or in the maintenance and inspection of the camera.
More particularly, the invention relates to a various camera data confirming device which utilizes the electrical contacts normally used for inputting DX code so that camera exposure data can be externally confirmed.
2. Background Art
Recently, the automation of camera operations has been remarkably advanced. Therefore, various data for exposure calculation, automatic film winding, automatic ASA sensitivity reading, and a variety of displays are digitized. For instance, in an aperture-priority automatic exposure system, a set aperture value, a field brightness value and a film sensitivity (speed) value are converted into digital data to perform a predetermined APEX (aperture priority exposure) operation. The resultant value of the calculation is converted into analog data to control the shutter speed. However, the brightness value may include an error due to the position of the installed light receiving element or an electrical offset of the A/D conversion circuit. Therefore, during inspection of a camera being assembled, it is necessary to electrically eliminate the error, especially the offset error.
In order to transmit the film speed used to the arithmetic circuit in the camera, the following means has been proposed (cf. Japanese Patent Application "OPI" No. 211027/1984, the term "OPI" as used herein means an "unexamined published application"). As shown in FIGS. 1 and 2, selected conductive layers and non-conductive layers are formed at predetermined positions 10a, 10b, 10c, 10d and 10e on the outside of a film cartridge (patrone) 10 according to the sensitivity value of the film. Electrical contacts 12a, 12b, 12c, 12d and 12e are provided in the film cartridge receiving chamber of the camera in such a manner that, when the film cartridge 10 is loaded in the chamber, the conductive and nonconductive layers are brought into contact with the electrical contacts 12a-12e. In this case, an arithmetic circuit in the camera can automatically read the film sensitivity value according to the variation in the combination of the electrical signals conducted through the conductive film cartridge 1 along paths between the contacts 12a through 12d and the grounded electrical contact 12e.
If the circuit operation is carried out with digital data which has been converted from a analog data, it is essential to adjust its A/D conversion circuit and especially the offset value of the A/D conversion circuit. On the other hand, an exposure control circuit employs a method in which, for instance in the case of an aperture-priority automatic exposure system, after necessary electronic circuits including a light receiving element are installed on the camera body, an exposure determination is actually carried out to determine whether or not the aperture value Av and the field brightness value Bv are correctly calculated. A determination of the exposure permits the adjustment of the circuit. However, if, in the method, the values Av and Bv have their errors in opposite directions, these errors, being cancelled out, do not appear in the exposure value. The only method of detecting these errors is to perform the exposure calculation several times under different conditions so that the circuit may be adjusted as a whole. As the digital circuit for exposure operation is generally realized with a micro-computer, it is rather difficult to check the individual digital data. Even in the case where the individual digital signal lines can be monitored from the outside, the circuit itself is considerably small, and therefore it is difficult to suitably position a signal probe and to do so without damaging the circuit.
In the case of a camera, the aforementioned electronic circuits are enclosed in the camera housing, and therefore it is completely impossible to perform the maintenance and inspection for variations of the offset error or the like.